SITE INFORMATION AND CORRESPONDENCE

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4%� Thrifty Oil Company#171 page 2 1250 N. Wilson Way, Stockton CA May 4, 2010 106,000 micrograms per liter (ug/1). Groundwater concentrations of dissolved TPHg since the 2008/2009 GWE test have dropped significantly. The last concentration of TPHg noted on Geotracker is from the December 2009 sampling event and lists the highest TPHg groundwater concentration at 31,600 ug/I from monitoring/extraction well EW-5D. The other two wells located in the dissolved contaminant plume and proposed as groundwater extraction points, EW-5S and TB-7, reported TPHg at 1,610 ugll and 6,600 ug/l, respectively for the same sampling event. The EHD has concerns that extracting groundwater from these three wells at a combined extraction rate of 0.3 gpm may not be as effective against the mass as TOC has concluded. The EHD requires that a pilot groundwater extraction test be conducted utilizing the parameters included in the FS-WP. A full scale GWE action from all the wells proposed should be conducted for an adequate time to gather sufficient data to support conclusions that this GWE rate and treatment will reduce the contamination at the site in the time estimated by TOC. The report of findings should include an evaluation of the mass removal rate compared to the total residual mass. A work plan for the GWE pilot test is to be submitted to Geotracker by June 30, 2010. The complete FS-WP evaluation and approval is on hold and pending results of the GWE pilot test. If you have any questions, please contact Michael Infurna at (209)468-3454. 71 Michael J. Infuma Jr., REHS Nuel C. Henderson Jr., PG Senior Registered Environmental Health Specialist Engineering Geologist c: Mr. James L. Barton, CVRWQCB, Underground Storage Tank Unit, 11020 Sun Center Drive, #200, Rancho Cordova, CA 95670-6114 Mr. Mark Owens, SWRCB, Division of Clean Water Programs, Underground Storage Tank Program, P.O. Box 944212, Sacramento, CA 94244-2120